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Subject[PATCH 5.15 003/128] ext4: prevent partial update of the extent blocks
Date
From: Zhang Yi <yi.zhang@huawei.com>

commit 0f2f87d51aebcf71a709b52f661d681594c7dffa upstream.

In the most error path of current extents updating operations are not
roll back partial updates properly when some bad things happens(.e.g in
ext4_ext_insert_extent()). So we may get an inconsistent extents tree
if journal has been aborted due to IO error, which may probability lead
to BUGON later when we accessing these extent entries in errors=continue
mode. This patch drop extent buffer's verify flag before updatng the
contents in ext4_ext_get_access(), and reset it after updating in
__ext4_ext_dirty(). After this patch we could force to check the extent
buffer if extents tree updating was break off, make sure the extents are
consistent.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20210908120850.4012324-4-yi.zhang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/extents.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -136,15 +136,25 @@ int ext4_datasem_ensure_credits(handle_t
static int ext4_ext_get_access(handle_t *handle, struct inode *inode,
struct ext4_ext_path *path)
{
+ int err = 0;
+
if (path->p_bh) {
/* path points to block */
BUFFER_TRACE(path->p_bh, "get_write_access");
- return ext4_journal_get_write_access(handle, inode->i_sb,
- path->p_bh, EXT4_JTR_NONE);
+ err = ext4_journal_get_write_access(handle, inode->i_sb,
+ path->p_bh, EXT4_JTR_NONE);
+ /*
+ * The extent buffer's verified bit will be set again in
+ * __ext4_ext_dirty(). We could leave an inconsistent
+ * buffer if the extents updating procudure break off du
+ * to some error happens, force to check it again.
+ */
+ if (!err)
+ clear_buffer_verified(path->p_bh);
}
/* path points to leaf/index in inode body */
/* we use in-core data, no need to protect them */
- return 0;
+ return err;
}

/*
@@ -165,6 +175,9 @@ static int __ext4_ext_dirty(const char *
/* path points to block */
err = __ext4_handle_dirty_metadata(where, line, handle,
inode, path->p_bh);
+ /* Extents updating done, re-set verified flag */
+ if (!err)
+ set_buffer_verified(path->p_bh);
} else {
/* path points to leaf/index in inode body */
err = ext4_mark_inode_dirty(handle, inode);

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